✨ Add String.trimStart and String.trimEnd functions

string/mod.ts

@@ -8,3 +8,5 @@ export { trimRight } from "./trim_right.ts";
 export { toLowerCase } from "./to_lower_case.ts";
 export { toUpperCase } from "./to_upper_case.ts";
 export { repeat } from "./repeat.ts";
+export { trimEnd } from "./trim_end.ts";
+export { trimStart } from "./trim_start.ts";

string/trim_end.ts

@@ -0,0 +1,54 @@
+// Copyright 2021-present the Core-fn authors. All rights reserved. MIT license.
+import { Space } from "../deps.ts";
+
+/**
+ * Infer the string with the right ends of trimmed.
+ *
+ * @typeParam T - Any string
+ * @returns String right ends of trimmed
+ *
+ * @remarks
+ * The definition of space
+ * - `''`
+ * - `\n`
+ * - `\t`
+ *
+ * @example
+ * ```ts
+ * TrimEnd<'hello \n\t'> // 'hello'
+ * ```
+ *
+ * @category `String`
+ *
+ * @beta
+ */
+type TrimEnd<T extends string> = T extends `${infer R}${Space}` ? TrimEnd<R>
+  : T;
+
+/**
+ * Removes space from right ends of the string.
+ *
+ * @param val - input string
+ * @returns The result of `val.trimEnd()`
+ *
+ * @remarks
+ * The definition of space
+ * - `''`
+ * - `\n`
+ * - `\t`
+ *
+ * @example
+ * ```ts
+ * trimEnd('hello   ') // 'hello'
+ * trimEnd('hello \n\t') // 'hello'
+ * ```
+ *
+ * @category `String`
+ *
+ * @beta
+ */
+const trimEnd = <T extends string>(val: T): TrimEnd<T> =>
+  val.trimEnd() as TrimEnd<T>;
+
+export { trimEnd };
+export type { TrimEnd };

string/trim_right_test.ts → string/trim_end_test.ts

@@ -1,8 +1,8 @@
 // Copyright 2021-present the Core-fn authors. All rights reserved. MIT license.
 import { assertEquals, assertEqualsType } from "../dev_deps.ts";
-import { TrimRight, trimRight } from "./trim_right.ts";
+import { TrimEnd, trimEnd } from "./trim_end.ts";
 
-Deno.test("trimRight", () => {
+Deno.test("trimEnd", () => {
   const table: [string, string][] = [
     ["", ""],
     ["         ", ""],
@@ -17,14 +17,14 @@ Deno.test("trimRight", () => {
     ["   hello  world\n\n", "   hello  world"],
   ];
   table.forEach(([val, expected]) => {
-    assertEquals(trimRight(val), expected, `trimRight(${val}) -> ${expected}`);
+    assertEquals(trimEnd(val), expected, `trimEnd(${val}) -> ${expected}`);
   });
 
-  assertEqualsType<"", TrimRight<"">>();
-  assertEqualsType<"hello", TrimRight<"hello">>();
-  assertEqualsType<"", TrimRight<"\n">>();
-  assertEqualsType<"", TrimRight<"\t">>();
-  assertEqualsType<"", TrimRight<"\t\n ">>();
-  assertEqualsType<"hello", TrimRight<"hello ">>();
-  assertEqualsType<"\n\t hello", TrimRight<"\n\t hello\n\t ">>();
+  assertEqualsType<"", TrimEnd<"">>();
+  assertEqualsType<"hello", TrimEnd<"hello">>();
+  assertEqualsType<"", TrimEnd<"\n">>();
+  assertEqualsType<"", TrimEnd<"\t">>();
+  assertEqualsType<"", TrimEnd<"\t\n ">>();
+  assertEqualsType<"hello", TrimEnd<"hello ">>();
+  assertEqualsType<"\n\t hello", TrimEnd<"\n\t hello\n\t ">>();
 });

string/trim_start.ts

@@ -0,0 +1,53 @@
+// Copyright 2021-present the Core-fn authors. All rights reserved. MIT license.
+import { Space } from "../deps.ts";
+
+/**
+ * Infer the string with the left ends of trimmed.
+ *
+ * @returns String left ends of trimmed
+ *
+ * @remarks
+ * The definition of space
+ * - `''`
+ * - `\n`
+ * - `\t`
+ *
+ * @example
+ * ```ts
+ * TrimStart<' \n\thello'> // 'hello'
+ * ```
+ *
+ * @category `String`
+ *
+ * @beta
+ */
+type TrimStart<T extends string> = T extends `${Space}${infer R}` ? TrimStart<R>
+  : T;
+
+/**
+ * Removes the leading white space and line terminator characters from a string.
+ *
+ * @param val - input string
+ * @returns The result of `val.trimStart()`
+ *
+ * @remarks
+ * The definition of space
+ * - `''`
+ * - `\n`
+ * - `\t`
+ *
+ * @example
+ * ```ts
+ * trimStart('   hello') // 'hello'
+ * trimStart(' \n\thello') // 'hello'
+ * ```
+ *
+ * @category `String`
+ *
+ * @beta
+ */
+const trimStart = <T extends string>(val: T): TrimStart<T> =>
+  val.trimStart() as TrimStart<T>;
+
+export { trimStart };
+export type { TrimStart };

string/trim_left_test.ts → string/trim_start_test.ts

@@ -1,8 +1,8 @@
 // Copyright 2021-present the Core-fn authors. All rights reserved. MIT license.
 import { assertEquals, assertEqualsType } from "../dev_deps.ts";
-import { TrimLeft, trimLeft } from "./trim_left.ts";
+import { TrimStart, trimStart } from "./trim_start.ts";
 
-Deno.test("trimLeft", () => {
+Deno.test("trimStart", () => {
   const table: [string, string][] = [
     ["", ""],
     ["         ", ""],
@@ -17,14 +17,14 @@ Deno.test("trimLeft", () => {
     ["   hello  world\n\n", "hello  world\n\n"],
   ];
   table.forEach(([val, expected]) => {
-    assertEquals(trimLeft(val), expected, `trimLeft(${val}) -> ${expected}`);
+    assertEquals(trimStart(val), expected, `trimStart(${val}) -> ${expected}`);
   });
 
-  assertEqualsType<"", TrimLeft<"">>();
-  assertEqualsType<"hello", TrimLeft<"hello">>();
-  assertEqualsType<"", TrimLeft<"\n">>();
-  assertEqualsType<"", TrimLeft<"\t">>();
-  assertEqualsType<"", TrimLeft<"\t\n ">>();
-  assertEqualsType<"hello ", TrimLeft<"hello ">>();
-  assertEqualsType<"hello\n\t ", TrimLeft<"\n\t hello\n\t ">>();
+  assertEqualsType<"", TrimStart<"">>();
+  assertEqualsType<"hello", TrimStart<"hello">>();
+  assertEqualsType<"", TrimStart<"\n">>();
+  assertEqualsType<"", TrimStart<"\t">>();
+  assertEqualsType<"", TrimStart<"\t\n ">>();
+  assertEqualsType<"hello ", TrimStart<"hello ">>();
+  assertEqualsType<"hello\n\t ", TrimStart<"\n\t hello\n\t ">>();
 });